Who makes the brakes on the show car. They look like 4 piston calipers. Also will CTS-V brakes fit the G8?

Most likely Bosche - they make the HSV versions. The HSV brakes are all 4 pot.
For more info, go to www.hsv.com.au, click cars, then GTS, then brakes, the show brakes. This has a video stream.

Once you purchase your G8 (hint, hint), one Australian company might have a brake system exactly like the show car. Keep your eyes on this site: http://www.jhp.com.au

Correction - HSV premium brakes are 6 piston.

Still only VZ stuff on here

http://www.jhp.com.au/performance-brakes.php

Do they not post prices on their site?

I'm sure that once we start seeing G8s on the road, they will provide upgrades. Plus, they may offer parts, but not redesign the website. When they start getting to showrooms, ask me for an email address for one of the guys at JHP. They are good to their customers.

The only thing I'm concerned with is how much shipping a brake kit would cost.

Fedex quotes $350 for a 25 pound package, and $525 for a 55 pound package!